Underwater polishing system and underwater polishing method

ABSTRACT

An underwater polishing system according to the present disclosure includes a tank, a robot, and a polishing machine. In a state where a workpiece held by an arm portion of the robot, at least a part of a second rotating roller and at least a part of a polishing tool of the polishing machine are immersed in a liquid stored in the tank, the held workpiece is polished by operating the arm portion of the robot and pressing the held workpiece against the polishing tool.

The present application is based on, and claims priority from JP Application Serial Number 2021-043202, filed Mar. 17, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to an underwater polishing system and an underwater polishing method.

2. Related Art

As a polishing device, as described in JP-A-2016-132063, a device is known which performs polishing by circularly driving a belt-shaped sandpaper and bringing the belt-shaped sandpaper into contact with a surface of a polishing object on a mount. On the other hand, in a manufacturing process of a semiconductor device, a method of performing polishing and cutting in a liquid is also known (for example, refer to JP-A-2006-24910 and JP-A-2017-94455).

In a dry polishing manner, brown burn occurs due to friction heat, it is difficult to reduce the surface roughness of the polished surface, and polishing quality and productivity cannot be improved at the same time.

SUMMARY

According to one aspect of the present disclosure, an underwater polishing system is provided. The underwater polishing system includes: a tank that is configured to store a liquid; a robot that includes an arm portion configured to hold a workpiece, which is an object to be machined, and that is configured to operate the arm portion and move at least a part of the held workpiece from an outside of the tank into the liquid stored in the tank and from the liquid stored in the tank to the outside of the tank; and a polishing machine that includes a first rotating roller, a second rotating roller, and a polishing tool bridged to the first rotating roller and the second rotating roller, and in which at least a part of the second rotating roller and at least a part of the polishing tool are immersed in the liquid stored in the tank. In a state where the workpiece held by the arm portion of the robot, at least a part of the second rotating roller and at least a part of the polishing tool of the polishing machine are immersed in the liquid stored in the tank, the held workpiece is polished by operating the arm portion of the robot and pressing the held workpiece against the polishing tool.

According to one aspect of the present disclosure, an underwater polishing method is provided. The underwater polishing method includes: a workpiece holding step of holding, by an arm portion of a robot, a workpiece, which is an object to be machined; a polishing machine driving step of driving a polishing tool that is bridged to a first rotating roller and a second rotating roller of a polishing machine; a liquid storing step of storing a liquid in a tank; and a polishing step of polishing the held workpiece by operating the arm portion of the robot and pressing the held workpiece against the polishing tool, in a state where the workpiece held by the arm portion of the robot, at least a part of the second rotating roller and at least a part of the polishing tool of the polishing machine are immersed in the liquid stored in the tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an underwater polishing system according to a first embodiment.

FIG. 2 is a functional block diagram of a control unit.

FIG. 3 is an enlarged view showing a periphery of a polishing point.

FIG. 4 is a diagram showing an underwater polishing system according to a second embodiment.

FIG. 5 is a diagram showing an underwater polishing system according to a third embodiment.

FIG. 6 is a diagram showing a modification of the third embodiment.

FIG. 7 is a diagram showing an underwater polishing system according to a fourth embodiment.

FIG. 8 is an enlarged view showing a main part of a measuring mechanism.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

FIG. 1 is a diagram showing an underwater polishing system according to a first embodiment. FIG. 2 is a functional block diagram of a control unit. FIG. 3 is an enlarged view showing a periphery of a polishing point.

An underwater polishing system 1 shown in FIG. 1 includes a tank 10, a robot 30, a polishing machine 50, and a control unit 70.

In the embodiment, the tank 10 is a container that is open to an upper side and that has a rectangular parallelepiped shape. The tank 10 can store a liquid L therein. In the embodiment, the liquid L is water. A liquid other than water can also be used as the liquid L. A shape of the tank 10 is not particularly limited, but is a shape capable of performing a required liquid storing function in the underwater polishing system 1.

The robot 30 includes an arm portion 31 that holds a workpiece W, which is an object to be machined, and a base portion 32 that supports the arm portion 31. The robot 30 according to the embodiment is a 6-axis articulated robot. That is, the arm portion 31 is an articulated arm having six articulated axes of a first axis to a sixth axis from the base portion 32 side. An articulated axis that has been publicly known can be used as the arm portion 31.

The arm portion 31 has an arm portion body 33 in which a plurality of arms are coupled via articulated axes, a force sensor 34 attached to a tip end portion of the arm portion body 33, and a robot hand 35 attached to a tip side of the force sensor 34. The arm portion body 33 is coupled to the base portion 32 via the first axis. The robot hand 35 holds the workpiece W so that the workpiece W can be transferred. The robot hand 35 holds the workpiece W by gripping or sucking the workpiece W. The force sensor 34 detects an external force acting on the robot hand 35. A detected value of the force sensor 34 is output to the control unit 70.

The robot 30 operates the arm portion 31 to move the held workpiece W inside and outside the tank 10. That is, the robot 30 moves at least a part of the held workpiece W from an outside of the tank 10 into the liquid L stored in the tank 10. The robot 30 also moves at least a part of the held workpiece W from the liquid L stored in the tank 10 to the outside of the tank 10.

A part that is immersed in the liquid L and a part that may be in contact with the liquid L, of the robot 30, are subjected to a necessary waterproofing treatment in accordance with the part. For example, the robot hand 35 and the force sensor 34 that are immersed in the liquid L and the tip end portion of the arm portion body 33 that may be immersed in the liquid L have dustproof and waterproof performance of IP67 grade specified in, for example, International Electrotechnical Commission (IEC) and Japanese Industrial Standards (JIS). The waterproof performance is a performance allowing the workpiece W to be immersed in the liquid L to a desired depth. On the other hand, a part not immersed in the liquid L, such as a base end side of the arm portion body 33, may have a relatively low waterproof performance.

The polishing machine 50 includes a first rotating roller 51, a second rotating roller 52, a polishing tool 53, a belt arm 54, and a polishing machine body 55. The belt arm 54 is coupled to the polishing machine body 55 on one side end portion in a lengthwise direction. The belt arm 54 can rotate around a rotating axis that is located at a coupling portion between the belt arm 54 and the polishing machine body 55.

The first rotating roller 51 and the second rotating roller 52 are attached to both ends of the belt arm 54 in the lengthwise direction, respectively. The first rotating roller 51 is located in a vicinity of the coupling portion between the belt arm 54 and the polishing machine body 55. The second rotating roller 52 is located at the tip end portion of the belt arm 54. The first rotating roller 51 and the second rotating roller 52 can rotate around a rotating axis extending in a direction orthogonal to the lengthwise direction of the belt arm 54. A rotating axis J1 of the first rotating roller 51 and a rotating axis J2 of the second rotating roller 52 are disposed parallel to each other.

The polishing tool 53 is an endless belt and is stretched between the first rotating roller 51 and the second rotating roller 52 with a predetermined tension. The polishing tool 53 has a belt-shaped substrate and abrasive grains fixed to one surface of the substrate. The polishing tool 53 is hung on the first rotating roller 51 and the second rotating roller 52 such that the surface to which the abrasive grains are fixed facing outward.

The polishing machine body 55 includes a driving mechanism 56 that drives the polishing tool 53. In the embodiment, the driving mechanism 56 of the polishing machine body 55 is a motor that rotationally drives the first rotating roller 51. The polishing tool 53 is circularly driven by the rotation of the first rotating roller 51. The second rotating roller 52 rotates with traveling of the polishing tool 53. That is, in the embodiment, the first rotating roller 51 is a driving roller and the second rotating roller 52 is a driven roller.

The polishing machine 50 is used in a state where a part of the workpiece W that is subjected to be polished is immersed in the liquid L stored in the tank 10. In the embodiment, as shown in FIG. 1, at least a part of the second rotating roller 52 and at least a part of polishing tool 53 of the polishing machine 50 are immersed in the liquid L. In the embodiment, the second rotating roller 52 immersed in the liquid L is a driven roller having no electrical components, and thus a waterproof structure for protecting the electrical components is unnecessary. It is unnecessary to add a configuration for underwater polishing to the polishing machine 50, and it is possible to inhibit the complexity and cost increase in the polishing machine 50.

The control unit 70 integrally controls the underwater polishing system 1. The control unit 70 is coupled to the robot 30 and the polishing machine 50. The robot 30 includes a robot control unit 71 that functions as a slave device of the control unit 70. The polishing machine 50 includes a polishing machine control unit 72 that functions as a slave device of the control unit 70.

As shown in FIG. 2, the control unit 70 and the robot control unit 71 are coupled to each other so as to be able to communicate with each other, and the control unit 70 and the polishing machine control unit 72 are coupled to each other so as to be able to communicate with each other. The robot control unit 71 is coupled to the arm portion 31, the force sensor 34, and the robot hand 35 of the robot 30 via a bus 71 a, and controls an operation of the robot 30. The polishing machine control unit 72 is coupled to the driving mechanism 56 via a bus 72 a, and controls an operation of the polishing machine 50. FIG. 2 shows only the configuration necessary for explanation.

As shown in FIG. 1, the underwater polishing system 1 including the above configuration polishes the workpiece W in a state where the second rotating roller 52 of the polishing machine 50 and the workpiece W are immersed in the liquid L stored in the tank 10.

An underwater polishing method according to the embodiment includes: a workpiece holding step of holding, by the arm portion 31 of the robot 30, the workpiece W, which is an object to be machined; a polishing machine driving step of driving the polishing tool 53 that is bridged to the first rotating roller 51 and the second rotating roller 52 of the polishing machine 50; a liquid storing step of storing the liquid L in the tank 10; and a polishing step of polishing the held workpiece W by operating the arm portion 31 of the robot 30 and pressing the held workpiece W against the polishing tool 53, in a state where the workpiece W held by the arm portion 31 of the robot 30, and at least a part of the second rotating roller 52 and at least a part of the polishing tool 53 of the polishing machine 50 are immersed in the liquid L stored in the tank 10.

In the workpiece holding step, the control unit 70 outputs a command for moving the workpiece W to a polishing position to the robot 30. Under the control of the robot control unit 71, the robot 30 operates the arm portion 31 and picks up the workpiece W from a workpiece supplying position (not shown) using the robot hand 35. The robot 30 moves the workpiece W held by the robot hand 35 into the liquid L.

In the polishing machine driving step, the control unit 70 operates the polishing machine 50. The control unit 70 outputs a command for causing the polishing tool 53 to travel to the polishing machine control unit 72. Under the control of the polishing machine control unit 72, the polishing machine 50 rotates the first rotating roller 51 by the driving mechanism 56 and circularly drives the polishing tool 53.

In the polishing step, the robot 30 brings the workpiece W into contact with the polishing tool 53 in the liquid L. Thus, as shown in FIG. 3, in the liquid L, a predetermined position of the workpiece W is in contact with the polishing tool 53, and the workpiece W is polished by the polishing tool 53. At this time, a position where the workpiece W and the polishing tool 53 are in contact with each other is a polishing point P. In the embodiment, the polishing point P is an apex position where the second rotating roller 52 protrudes farthest in a horizontal direction in the liquid L. The polishing of the workpiece W is performed while the robot 30 moves the workpiece W from a lower side toward an upper side of the polishing point P.

The control unit 70 controls the workpiece W to be polished for a period until a preset end condition is satisfied. The above end condition is, for example, a lapse of a predetermined polishing time, satisfaction of a setting value of a detected value of the force sensor 34, or a stoppage due to an error.

The robot 30 measures, by the force sensor 34, the external force acting on the robot hand 35 during the polishing. The detected value measured by the force sensor 34 is output to the control unit 70 from the robot control unit 71. The control unit 70 manages a state of a polishing treatment based on the detected value of the force sensor 34. For example, based on the detected value of the force sensor 34, the control unit 70 controls the workpiece W to be pressed against the polishing tool 53 with a predetermined force.

The control unit 70 may be able to adjust conditions of the polishing treatment based on the detected value of the force sensor 34. The conditions of the polishing treatment are, for example, a posture of the workpiece W, a part of the workpiece W in contact with the polishing tool 53, a pressing force of the workpiece W against the polishing tool 53, a position of the polishing point P on the polishing tool 53, a traveling speed of the polishing tool 53, and the like. For example, when an excessive load is detected, the control unit 70 may change the polished part or the posture of the workpiece W, or stop the polishing treatment.

When a predetermined polishing treatment is completed, the control unit 70 controls the workpiece W to be moved from the liquid L to the outside of the tank 10. The control unit 70 controls the workpiece W to be moved to a workpiece discharging position (not shown) of the underwater polishing system 1.

Accordingly, the polishing step of the workpiece W is completed.

In the underwater polishing system 1 according to the embodiment, the polishing is performed by bringing the polishing tool 53, which is bridged between the first rotating roller 51 and the second rotating roller 52, and the workpiece W that is to be polished into contact with each other in the liquid L. According to this configuration, the polishing is performed in a liquid that has a high cooling efficiency, thereby inhibiting a temperature increase due to a friction between the polishing tool 53 and the workpiece W. The workpiece W can be pressed against the polishing tool 53 with a stronger force, and thus a polishing rate can be increased and a treatment efficiency can be improved. Further, by polishing in the liquid L, chips generated by polishing the workpiece W are less likely to be fixed onto a surface of the polishing tool 53. The polishing can be performed with the polishing tool 53 in a state where there is little adhesion of chips, and thus a polished surface of the workpiece W is less likely to be scratched, and a surface roughness of the polished surface can be reduced. Since a quality of the polished surface is improved, there is a possibility that the polishing treatment, which requires two steps of rough polishing and finish-polishing in the related art, can be performed in one step.

In the embodiment, the tip end portion of the belt arm 54 that includes the second rotating roller 52 is immersed in the liquid L, but as long as the polishing point P shown in FIG. 3 is located in the liquid L, a function and effect as described above can be achieved. For example, a part of each of the second rotating roller 52 and the workpiece W, which is located above the polishing point P, may be exposed upward from a liquid surface of the liquid L. Therefore, in the state where the workpiece W, and the second rotating roller 52 and at least a part of the polishing tool 53 of the polishing machine 50 are immersed in the liquid L, the held workpiece W is polished by operating the arm portion 31 of the robot 30 and pressing the held workpiece W against to a part of the polishing tool 53 located in the liquid L. In other embodiments to be described later, a part of the workpiece W or the polishing tool 53 can be placed outside the liquid L as long as there is no inconsistency in the configuration.

Second Embodiment

FIG. 4 is a diagram showing an underwater polishing system according to a second embodiment. Among the components shown in FIG. 4, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description of the components will be simplified.

The underwater polishing system 1 shown in FIG. 4 includes the tank 10, the robot 30, a polishing machine 50A, and the control unit 70.

The polishing machine 50A includes the first rotating roller 51, the second rotating roller 52, the polishing tool 53, the belt arm 54, the polishing machine body 55, a first pulley 57 a, a second pulley 57 b, an extended arm 58, a driving belt 59, and a polishing table 60.

The first pulley 57 a is coupled to the driving mechanism 56 of the polishing machine body 55. The extended arm 58 extends downward from a coupling position between the first pulley 57 a and the driving mechanism 56. An upper end portion of the extended arm 58 is fixed to a housing of the polishing machine body 55. One end portion of the belt arm 54 is coupled to a lower end portion of the extended arm 58. The belt arm 54 is rotatable about the coupling position between the belt arm 54 and the extended arm 58.

The first rotating roller 51 and the second pulley 57 b are attached to an end portion of the belt arm 54 on the extended arm 58 side. The first rotating roller 51 and the second pulley 57 b are fixed to each other and rotate together around the rotating axis J1. The driving belt 59 is bridged between the first pulley 57 a and the second pulley 57 b. The driving belt 59 is an endless belt.

The second rotating roller 52 is attached to the tip end portion of the belt arm 54. The polishing tool 53 is bridged between the first rotating roller 51 and the second rotating roller 52.

The polishing table 60 is fixed to a central portion of the belt arm 54 in the lengthwise direction. The polishing table 60 is located between the polishing tool 53 and the belt arm 54. The polishing table 60 has a tool supporting surface 60 a that faces an inner side surface of the polishing tool 53. The polishing tool 53 slides on the tool supporting surface 60 a during traveling.

The driving mechanism 56 of the polishing machine body rotationally drives the first pulley 57 a. Therefore, the driving belt 59 is circularly driven, and the second pulley 57 b rotates. Therefore, the first rotating roller 51 fixed to the second pulley 57 b rotates around the rotating axis J1. Through a rotation of the first rotating roller 51, the polishing tool 53 is circularly driven, and the second rotating roller 52 rotates around the rotating axis J2.

The polishing machine 50A performs a polishing in a state where the belt arm 54, the first rotating roller 51, the second rotating roller 52, and the polishing tool 53 are entirely immersed in the liquid L. The robot 30 brings the held workpiece W into contact with the polishing tool 53 that travels by a power of the driving mechanism 56. In the embodiment, the polishing point P where the workpiece W and the polishing tool 53 are in contact with each other is located on the tool supporting surface 60 a of the polishing table 60. By supporting the polishing tool 53 with the polishing table 60, it is possible to inhibit the polishing tool 53 from bending at the polishing point P, and the workpiece W can be polished with high accuracy.

In the underwater polishing system 1 according to the embodiment, the polishing tool 53 performs a polishing in the state where the entire polishing tool 53 is immersed in the liquid L, and thus the polishing tool 53 is always in contact with the liquid L, and chips adhering to the surface can be easily removed. Since the polishing tool 53 does not run out of the liquid L, it is possible to inhibit scattering of the liquid L and chips due to the polishing tool 53.

The driving belt 59 enters in and exits from the liquid L, but the endless belt thinner than the polishing tool 53 can be used as the driving belt 59, and thus less liquid L and chips are wound up by the traveling of the driving belt 59. Further, the driving belt 59 is not in contact with the workpiece W, and thus even a cover for scattering prevention is attached to the driving belt 59, the polishing can be performed without any problem.

Third Embodiment

FIG. 5 is a diagram showing an underwater polishing system according to a third embodiment. Among the components shown in FIG. 5, the same components as those in the first embodiment and the second embodiment are denoted by the same reference numerals as those in the first embodiment and the second embodiment, and the description of the components will be simplified.

The underwater polishing system 1 shown in FIG. 5 includes a tank 10A, the robot 30, the polishing machine 50A, and the control unit 70.

The tank 10A includes a tank body 10 a that is open to an upper side and that has a box shape, a circulating pipe 11 that is open to two points on a bottom surface of the tank body 10 a, a pump 12 and a filter 13 that are located on a path of the circulating pipe 11, a straightening plate 14 that is located in the tank body 10 a, and a tank control unit 73 that controls an operation of the tank 10A.

The liquid L is stored in the tank body 10 a. The tank body 10 a is divided into two regions 101 and 102 by the straightening plate 14. The entire polishing tool 53 of the polishing machine 50A is immersed in the liquid L stored in the region 101 of the tank body 10 a.

The circulating pipe 11 has a first pipe 11 a that is open to a bottom surface of the tank body 10 a in the region 101, a second pipe 11 b that is open to the bottom surface in the region 102, and a third pipe 11 c that couples the first pipe 11 a and the second pipe 11 b. The first pipe 11 a and the third pipe 11 c are coupled via the filter 13. The second pipe 11 b and the third pipe 11 c are coupled via the pump 12.

The first pipe 11 a is a funnel-shaped pipe whose diameter increases toward an opening end on the tank body 10 a side. The second pipe 11 b and the third pipe 11 c are pipes that have uniform inner diameters along directions in which the second pipe 11 b and the third pipe 11 c extend, respectively.

In the embodiment, the tank control unit 73 drives and controls the pump 12. The tank control unit 73 can communicate with the control unit 70. The tank control unit 73 functions as a slave device of the control unit 70. The tank control unit 73 may be able to control other electronic devices (for example, supplying valve, discharging valve, heater, and the like) installed in the tank 10A.

In the underwater polishing system 1 according to the embodiment, it is possible to polish the workpiece W while circulating the liquid L in the tank 10A.

In the polishing step of the workpiece W, the operations of the robot 30 and the polishing machine 50A are the same as those in the first embodiment and the second embodiment. In the polishing step, the control unit 70 outputs a command for driving the pump 12 to the tank control unit 73. In the tank 10A, under the control of the tank control unit 73, the liquid L in the circulating pipe 11 is pumped by the pump 12.

The pump 12 sucks the liquid L from the third pipe 11 c and discharges the liquid L to the second pipe 11 b. Therefore, in the tank 10A, the liquid L is sucked from the tank body 10 a to the first pipe 11 a. The liquid L in the first pipe 11 a passes through the filter 13, and then passes through the third pipe 11 c, the pump 12, and the second pipe 11 b, and returns to the tank body 10 a. The liquid L discharged from the bottom surface of the tank body 10 a in the region 102 is made uniform in a flow rate distribution by the straightening plate 14 and flows into the region 101. Therefore, as shown in FIG. 5, a flow wf of the liquid L along a traveling direction of the polishing tool 53 is formed in the polishing point P where the workpiece W and the polishing tool 53 are in contact with each other.

The control unit 70 drives the robot 30 and brings the workpiece W into contact with the polishing tool 53 in the liquid L to polish the workpiece W. At this time, since the flow wf of the liquid L in the same direction as the traveling direction of the polishing tool 53 is formed in the polishing point P where the workpiece W and the polishing tool 53 are in contact with each other, chips of the workpiece W flow away the polishing point P by the flow wf of the liquid L and the polishing tool 53.

As shown in FIG. 5, the flow wf of the liquid L uniformly flows to a left side in the drawing over a depth direction of the tank body 10 a due to an action of the straightening plate 14. Therefore, the chips flowed with the flow wf are sucked into the circulating pipe 11 from the opening of the first pipe 11 a without being caused to flow to the polishing point P side. The chips sucked into the circulating pipe 11 are collected by the filter 13 and do not return to the tank body 10 a.

In the underwater polishing system 1 according to the embodiment, a flow of the liquid L toward a traveling direction frontward side of the polishing tool 53 is formed in the polishing point P where the polishing tool 53 and the workpiece W are in contact with each other, so that the chips generated by polishing can be removed rapidly from the polishing point P. Therefore, it is possible to inhibit an occurrence of scratches and the like on the workpiece W due to chips, and to stabilize a surface roughness of a machined surface of the workpiece W.

In the embodiment, the tank 10A includes the filter 13, and thus the chips, desorbed abrasive grains, and other impurity particles contained in the liquid L that circulates in the tank 10A can be removed by the filter 13. Therefore, it is possible to inhibit entering of these particles into the polishing point P. It is possible to inhibit the occurrence of scratches and the like due to these particles. The liquid L is purified by the filter 13, and thus a service life of the liquid L can be extended.

FIG. 6 is a diagram showing a modification of the third embodiment.

As shown in FIG. 6, the underwater polishing system 1 according to the embodiment may have a tool cleaning mechanism 15 that cleans the polishing tool 53 in the tank 10A. In the embodiment, the tool cleaning mechanism 15 is a cylindrical rotating brush that extends along a rotating axis J3. The rotating axis J3 is parallel to the rotating axis J1 of the first rotating roller 51. The tool cleaning mechanism 15 including the rotating brush can rotate around the rotating axis J3. The rotating axis J3 is fixed to the tank 10A or the polishing machine 50A.

The tool cleaning mechanism 15 is located in a vicinity of the first rotating roller 51. The tool cleaning mechanism 15 is located at an opening portion of the first pipe 11 a on the bottom surface of the tank body 10 a. That is, the tool cleaning mechanism 15 is located upstream of the filter 13 (refer to FIG. 5) in a direction of flow of the liquid L in the tank 10A.

An outer peripheral surface of the tool cleaning mechanism 15 is in contact with a surface facing an outside of the polishing tool 53. In the embodiment, the tool cleaning mechanism 15 sandwiches the polishing tool 53 between the tool cleaning mechanism 15 and the first rotating roller 51. The tool cleaning mechanism 15 is rotated in a direction opposite to the first rotating roller 51 by the traveling polishing tool 53. As in the embodiment, the tool cleaning mechanism 15 may be the rotating brush that follows the traveling of the polishing tool 53, or may be a configuration including a driving mechanism such as a motor that rotates the rotating brush. When the rotating brush is rotated by the driving mechanism, the rotating brush may be rotated against the traveling of the polishing tool 53.

In the underwater polishing system 1 according to the modification, the chips adhering to the polishing tool 53 can be removed from the polishing tool 53 by the tool cleaning mechanism 15 that is in contact with the polishing tool 53. Therefore, it is possible to improve a cleanliness of the polishing tool 53, and to stabilize a polishing rate and the surface roughness of the machined surface of the workpiece W. The chips removed from the polishing tool 53 are sucked into the first pipe 11 a with the flow of the liquid L and collected by the filter 13.

Fourth Embodiment

FIG. 7 is a diagram showing an underwater polishing system according to a fourth embodiment. FIG. 8 is an enlarged view showing a main part of a measuring mechanism. Among the components shown in FIG. 7 and FIG. 8, the same components as those in the first embodiment to the third embodiment are denoted by the same reference numerals as those in the first embodiment to the third embodiment, and the description of the components will be simplified.

The underwater polishing system 1 shown in FIG. 7 includes the tank 10, the robot 30, the polishing machine 50A, a measuring mechanism 80, and the control unit 70.

The measuring mechanism 80 measures a polishing amount of the workpiece W. The measuring mechanism 80 includes a base 81, a slider 82, a measuring device 83, and a measuring device control unit 74. The base 81 is fixed on an upper surface of the polishing machine body 55. A fixing position of the base 81 is not limited to the polishing machine body 55. The slider 82 is provided on an upper surface of the base 81. The slider 82 is movable in the horizontal direction with respect to the base 81. The slider 82 supports the measuring device 83. The measuring device 83 is movable in the horizontal direction together with the slider 82.

The measuring device 83 includes a cylindrical cylinder 83 a that is supported by the slider 82 and extends in the horizontal direction, a rod 83 b that is movable forward and backward with respect to the cylinder 83 a, and a pad 83 c that is located on a tip end of the rod 83 b. A displacement measuring unit 83 d that detects a displacement of the rod 83 b is provided in the cylinder 83 a.

The measuring device 83 detects, by the displacement measuring unit 83 d in the cylinder 83 a, a movement in the horizontal direction of the rod 83 b due to an external force input to the pad 83 c. The measuring device control unit 74 acquires a detected value of the displacement measuring unit 83 d. The measuring device control unit 74 outputs, as a positional displacement amount of the rod 83 b (pad 83 c), a detected value of a gauge to the control unit 70.

In the embodiment, a positioning member 85 is attached to the polishing machine body 55 via a bracket 84. The positioning member 85 regulates a relative position of the workpiece W and the measuring mechanism 80. By bringing a predetermined position of the robot 30 into contact with the positioning member 85, a position of the workpiece W held by the robot hand 35 can be fixed with respect to the positioning member 85. Therefore, the workpiece W can be positioned with respect to the base 81 that is fixed to the polishing machine body 55 similarly to the positioning member 85. The bracket 84 and the positioning member 85 are high-rigidity members capable of inhibiting a deformation when the robot 30 is brought into contact with the bracket 84 and the positioning member 85. The bracket 84 and positioning member 85 are made of, for example, metal.

In the underwater polishing system 1 according to the embodiment, the polishing amount of the workpiece W held by the robot 30 can be measured by the measuring mechanism 80.

An underwater polishing method using the underwater polishing system 1 according to the embodiment includes a polishing step of polishing the workpiece W and a polishing amount measuring step of measuring the polishing amount of the workpiece W.

In the polishing treatment of the workpiece W, the control unit 70 controls the measuring mechanism 80 to measure a dimension before polishing of the workpiece W before the workpiece W is polished. The control unit 70 outputs a command for conveying the workpiece W to a measuring position shown in each of FIGS. 7 and 8 to the robot 30. The robot 30 places the workpiece W held by the robot hand 35 at a position where the workpiece W faces the pad 83 c of the measuring device 83 in the horizontal direction. At this time, the robot 30 brings the force sensor 34 into contact with the positioning member 85. The robot 30 adjusts the position of the workpiece W in the horizontal direction based on a detected value of the force sensor 34. That is, the force, with which the force sensor 34 is pressed against the positioning member 85, is controlled to be a preset value, so that the position of the workpiece W in the horizontal direction can be controlled with high repeatability and high accuracy.

After the workpiece W is placed at a predetermined measuring position, the measuring device 83 is placed at a measuring reference position by moving the slider 82 of the measuring mechanism 80. The slider 82 is fixed on the base 81 at the measuring reference position. The pad 83 c of the measuring device 83 located at the measuring reference position is in contact with a polished part of the workpiece W, and the rod 83 b is arranged at a position slightly pushed in from a position where the rod 83 b protrudes from the cylinder 83 a to a maximum extent. The measuring device control unit 74 outputs, to the control unit 70, the detected value of the displacement measuring unit 83 d in the measuring reference position. The control unit 70 stores, as an initial position (position before polishing) of the polished part of the workpiece W, the acquired detected value.

A movement of the slider 82 may be performed manually by a measurer, or may be performed a manner in which an electric slider or a linear motor is driven and controlled by the measuring device control unit 74.

After the measuring of the initial position of the workpiece W is completed, the control unit 70 controls the workpiece W to be polished. In the polishing step of the workpiece W, the operations of the robot 30 and the polishing machine 50A are the same as those in the first embodiment to the third embodiment.

After the polishing of the workpiece W is completed, the control unit 70 controls the measuring mechanism 80 to measure the polishing amount of the workpiece W. The control unit 70 outputs a command for moving the workpiece W to the measuring position to the robot control unit 71. Under the control of the robot control unit 71, the robot 30 brings the held workpiece W to be in contact with the pad 83 c of the measuring device 83. At this time, the robot 30 presses the force sensor 34 against the positioning member 85, and adjusts a position of the arm portion 31 such that the detected value of the force sensor 34 matches the detected value of the force sensor 34 before polishing. By adjusting the position of the workpiece W based on the detected value of the force sensor 34, the workpiece W can be accurately placed at the same position in two times of the measuring step before and after the polishing.

The rod 83 b is pushed toward the cylinder 83 a by pressing the workpiece W against the pad 83 c. The measuring device control unit 74 outputs, to the control unit 70, the detected value of the displacement measuring unit 83 d in the cylinder 83 a. The control unit 70 stores, as a machining position (position after the polishing) of the workpiece W, the acquired detected value of the displacement measuring unit 83 d.

The control unit 70 calculates the polishing amount (amount abraded by the polishing) of the workpiece W based on the initial position and the machining position of the workpiece W that are measured before and after the polishing. The control unit 70 determines whether to continue or end the polishing step based on the polishing amount of the workpiece W. For example, when the polishing amount of the workpiece W falls below a range that is set as a normal polishing amount range, the control unit controls the workpiece W to be polished again. When the polishing amount of the workpiece W is within the normal polishing amount range, the control unit 70 ends the polishing step and controls the workpiece W to be sorted as a non-defective product. Further, when the polishing amount of the workpiece W exceeds the normal polishing amount range, the control unit 70 ends the polishing step and controls the workpiece W to be sorted as a defective product.

In the underwater polishing system according to the embodiment, the polishing amount of the workpiece W can be measured, and thus it is possible to perform the polishing while grasping the polishing amount of the workpiece W, and to easily obtain a desired polishing amount. Further, the polishing amount can be measured while holding the workpiece W by the robot 30, and thus a positional displacement of the workpiece W due to attachment/detachment to/from the robot hand 35 does not occur, and the polishing amount can be measured multiple times with high accuracy.

In the embodiment, a case where a step of measuring the initial position of the polished part of the workpiece W before the polishing step is included has been explained, but for example, when a value of the initial position is known in advance, the measuring of the initial position is unnecessary. Further, when a variation in the initial positions in a plurality of the workpieces W is very small, only an initial position of a first workpiece W may be measured, and the first measured value may be used for the other workpieces W thereafter.

The configurations in the first embodiment to the fourth embodiment and the modification can be freely combined. For example, a system may be adopted, which includes the polishing machine 50 in the first embodiment and the tool cleaning mechanism 15 in the modification of the third embodiment. Alternatively, a system may be adopted, which includes the tank 10A in the second embodiment and the measuring mechanism 80 in the fourth embodiment. 

What is claimed is:
 1. An underwater polishing system, comprising: a tank that is configured to store a liquid; a robot that includes an arm portion configured to hold a workpiece, which is an object to be machined, and that is configured to operate the arm portion and move at least a part of the held workpiece from an outside of the tank into the liquid stored in the tank and from the liquid stored in the tank to the outside of the tank; and a polishing machine that includes a first rotating roller, a second rotating roller, and a polishing tool bridged to the first rotating roller and the second rotating roller, and in which at least a part of the second rotating roller and at least a part of the polishing tool are immersed in the liquid stored in the tank, wherein in a state where the workpiece held by the arm portion of the robot, at least a part of the second rotating roller and at least a part of the polishing tool of the polishing machine are immersed in the liquid stored in the tank, the held workpiece is polished by operating the arm portion of the robot and pressing the held workpiece against the polishing tool.
 2. The underwater polishing system according to claim 1, wherein the first rotating roller is a driving roller and the second rotating roller is a driven roller.
 3. The underwater polishing system according to claim 1, wherein the entire polishing tool is immersed in the liquid in the tank to perform polishing.
 4. The underwater polishing system according to claim 1, wherein a flow of the liquid toward a traveling direction frontward side of the polishing tool is formed in a polishing point where the polishing tool and the workpiece are in contact with each other.
 5. The underwater polishing system according to claim 1, further comprising: a circulating device configured to circulate the liquid in the tank; and a filter configured to purify the liquid circulating in the tank.
 6. The underwater polishing system according to claim 5, further comprising: a tool cleaning mechanism located upstream of the filter and configured to clean a surface of the polishing tool.
 7. The underwater polishing system according to claim 1, further comprising: a measuring mechanism configured to measure a polishing amount of the workpiece.
 8. The underwater polishing system according to claim 1, wherein the arm portion that holds the workpiece includes a force sensor.
 9. An underwater polishing method, comprising: a workpiece holding step of holding, by an arm portion of a robot, a workpiece, which is an object to be machined; a polishing machine driving step of driving a polishing tool that is bridged to a first rotating roller and a second rotating roller of a polishing machine; a liquid storing step of storing a liquid in a tank; and a polishing step of polishing the held workpiece by operating the arm portion of the robot and pressing the held workpiece against the polishing tool, in a state where the workpiece held by the arm portion of the robot, at least a part of the second rotating roller and at least a part of the polishing tool of the polishing machine are immersed in the liquid stored in the tank.
 10. The underwater polishing method according to claim 9, wherein in the polishing step, the first rotating roller, the second rotating roller, and the polishing tool of the polishing machine are immersed in the liquid.
 11. The underwater polishing method according to claim 9, wherein in the polishing step, a flow of the liquid toward a rotating direction frontward side of the second rotating roller is formed in a polishing point where the polishing tool and the workpiece are in contact with each other.
 12. The underwater polishing method according to claim 9, further comprising: a polishing amount measuring step of taking out the workpiece held by the arm portion of the robot from the liquid in the tank and measuring a polishing amount of the workpiece, after the polishing step.
 13. The underwater polishing method according to claim 12, further comprising: a pre-polishing measuring step of measuring a dimension before polishing of the workpiece held by the arm portion of the robot before the polishing step, wherein in the polishing amount measuring step, the polishing amount is calculated based on a result that is obtained in the pre-polishing measuring step. 